The classic game loop starts with a menu, waits for a user to start the game, runs the game until there is a winner, or the user abandons it, and then goes back to the menu.
Here we have hooked up keyboard events to allow the user to move the paddles up and down, start a 1 or 2 player game, and abandon the game in progress.
Press 1 for a single player game.
Press 2 for a double player game.
Press 0 to watch the computer play itself.
Player 1 moves using the Q and A keys.
Player 2 moves using the P and L keys.
Esc can be used to abandon a game.
NOTE: The paddles will be innefective until we implement collision detection in the next section.